Since its introduction in 1977, angioplasty has become a widely used procedure for the treatment of vascular disease. A common forms of angioplasty is coronary angioplasty, also known as “percutaneous transluminal coronary angioplasty,” in which a balloon catheter is inserted into a blocked artery to remove a stenosis.
During coronary angioplasty, the catheter is inserted into a blood vessel either at the elbow or at the groin. The catheter is then pushed inside the blood vessel until the point of blockage in the artery has been reached. A balloon disposed at the tip of the catheter then expands the narrowed artery and allows blood to flow normally through the artery after the procedure. Optionally, a stent is coupled to the balloon, so that the stent expands when the balloon is inflated, supporting the wall of the vessel after the balloon has been removed and maintaining patency.
A catheter suitable for angioplasty procedures must be sufficiently flexible to wind through tight curvatures, for example, in the coronary arteries, but at the same time must be “pushable,” or be able to transmit a longitudinal pressure along its length, so that a clinician can force the catheter through the vascular system and to the target location by applying a controlled amount of pressure at the proximal end of the catheter. The development of new materials has brought to market a new generation of catheters that provide the desired degree of “pushability” and trackability while enabling a considerable reduction in cross-sectional diameter.
A risk associated with catheters having an elevated degree of “pushability” is vessel injury or rupture. Additionally, a stiff catheter tip may cause endothelial abrasion by rubbing against the wall of the vessel.
To minimize these risks, catheters have been developed that include a soft distal tip, so to provide for a less traumatic contact with a vessel wall. Examples of prior art catheters having soft tips are disclosed U.S. Pat. No. 4,921,483 to Wijay et al.; U.S. Pat. No. 5,100,381 to Burns; U.S. Pat. No. 5,334,148 to Martin; U.S. Pat. No. 5,728,065 to Follmer et al.; U.S. Pat. No. 6,325,790 to Trotta; U.S. Pat. No. 6,368,301 and U.S. Pat. No. 6,837,869 to Hamilton et al.; U.S. Pat. No. 6,702,802 to Hancock et al.; U.S. Pat. No. 6,979,342 to Lee et al.; U.S. Pat. No. 6,999,809 to Currier et al.; and U.S. Pat. No. 7,115,137 to Duchamp. Such prior art catheters are manufactured by producing the tip as a separate component shaped for coupling with the catheter tube without discontinuities along the profile of the catheter, that is, without altering either the outer diameter or the lumen of the catheter, so that the insertion profile of the catheter is not modified and so that a guide wire reciprocating within the lumen does not encounter obstacles along its travel. The soft tips of those catheters are generally manufactured with a number of recesses that mate with the catheter body and with the distal end of the catheter balloon. Unfortunately, this process is costly because specially shaped tips must be produced and carefully coupled with the other components of the catheter, so that the various surfaces and recesses properly mate one with the other.